Karl Jansky Radio Telescope

How An Engineer Discovered The First Radio Waves Coming From The Milky Way About 90 Years Ago?

Karl Jansky, an American engineer and pioneer of Radio Astronomy, was born on 22nd October 1905 in Norman, Okla, United States. Also known as the father of radio astronomy whose discovery of radio waves from an extraterrestrial source inaugurated the development of radio astronomy, a new science that from mid 20th century vastly extended the range of astronomical observations. On the birth anniversary of Karl Jansky, here’s an article diving into his scientific life and contribution to an extraordinary impact on the world of astronomy.

Karl Jansky
Karl Jansky Credits: Wikipedia

Karl Jansky was third among six children, son of Cyril Jansky, an electrical engineering professor at the University of Wisconsin, who endured great love for physics in his three sons. He was named after physicist Karl Guthe whom his father had worked for earlier in his career. Karl Jansky earned his degree in physics from the University of Wisconsin.

He joined the research staff of Bell Telephone Laboratories in the year 1928. But Bell labs were initially reluctant to hire him as he was diagnosed with chronic kidney disease in college. Cyril Janksy Jr., an electrical engineer like his father and a former Bell Labs staff member who helped build some of the earliest radio transmitters in the U.S, interceded on his behalf.

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He was assigned a challenging task! The Bell Labs wanted to investigate atmospheric and ionospheric properties using ‘short waves’ (10- 20 meters) for use in trans-Atlantic radiotelephone service and as a radio engineer, Jansky was assigned to investigate and study intermittent static sources that might be interfering with a radio voice transmission. Now Jansky had to design and build special instruments for that purpose; a large directional antenna system mounted on a motor-driven turntable that rotated through 360º about a central vertical axis, riding on a circular track on the wheels of a Model-T Ford. Dubbed as “Jansky’s merry-go-round.

Karl Jansky
Karl Jansky with his “Merry Go Round” Radio Telescope. Credit: NRAO/AUI/NSF

After rigorous analysis of data that was collected over many tedious months – Jansky identified three types of static. A weak signal caused by distant thunderstorms, a more powerful burst due to local thunderstorms, and a third type which produced a steady hiss. The third he described as being “composed of very steady hiss static the origin of which is not yet known.” His careful wording came at the advice of his supervisor, who cautioned him against making over-bold claims.

But Jansky suspected that the signal originated in the center of the Milky Way galaxy, making it the first known detection of extraterrestrial radio signals. In the year 1933, in a journal article “Electrical disturbances apparently of extraterrestrial origin,” he referred to these electromagnetic waves detected causing the hiss belongs to an unknown origin.

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The reasonings were simple; he studied that the third type of static for over a year and noted that it rose and fell once a day. The very first conclusion was that it was radiation from the sun but after few months the brightest point of the signal moved away from the sun’s position, moreover, the rise and fall did not repeat exactly every 24 hours but every 2 hours and 56 minutes – a property of fixed stars and other celestial objects beyond our solar system. His strongest opinion based on this conclusion was that the most likely source of the radiation was the center of the Milky Way, where the signal was strongest in the constellation of Sagittarius.

The result was not one, but three published papers, including “Electrical disturbances apparently of extraterrestrial origin” (as mentioned previously), which he presented at a meeting of the International Scientific Radio Union in April 1933. This led to a high-profile news story in The New York Times on May 5th, 1933, trumpeting his discovery and the University awarded Jansky his master’s degree based on the three papers.

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To continue investigating these mysterious cosmic signals he wanted to build a 30-meter dish antenna for that purpose. But applied research was the centre of focus of Bell Labs. Since he showed that hissing static was not problematic for transatlantic communication, they judged the project complete and assigned Jansky another project.

He remained at Bell Labs for the rest of his career, toiling in relative obscurity despite pioneering a new field of science, although he was elected as a fellow of the Institute of Radio Engineers in 1948. But this new field of science didn’t emerge overnight, the dire economy and Jansky’s lack of professional standing as an astronomer dissuaded various observatories from investing in future research.

radio Telescope
Karl Jansky is regarded as one of the founding fathers of Radio Astronomy

Radio astronomy got a boost during World War II after the development of radar, an astronomer named John Kraus was able to start a radio observatory at Ohio State University. He eventually wrote a textbook that became the bible for radio astronomers. Radio astronomy by the year 1964 became an established branch – the year Arno Penzias and Robert Wilson used a giant horn antenna to discover the cosmic microwave background radiation.

Jansky died in the year 1950 at the age of 44 due to a massive stroke stemming from his kidney disease. Jansky’s work would most likely have won a Nobel Prize. Today the “Jansky” is the unit of measurement for radio wave intensity (flux density), a crater on the moon named after him, and the monument in his honor at the New Jersey site of his pivotal experiment.

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